Environmentally sustainable modifier-free, Zeeman-corrected graphite furnace atomic absorption spectrometry for trace cadmium determination in seawater and hypersaline brine

Accurate determination of trace cadmium (Cd) in seawater and hypersaline brine is analytically challenging because high dissolved salt concentrations cause severe matrix interferences during graphite furnace atomic absorption spectrometry (GFAAS). This study developed and validated an environmentally sustainable, modifier-free, Zeeman corrected GFAAS method based on matrix-specific furnace temperature optimization for reliable cadmium determination in high-salinity waters. Drying, pyrolysis, and atomization temperatures were systematically optimized for artificial seawater (ASW) and artificial brine (ABW) using a one-variable-at-a-time approach. The optimized furnace program employed drying at 150 °C, pyrolysis at 800 °C, and atomization at 1400 °C for seawater and 1500 °C for hypersaline brine. Zeeman background correction and sample dilution were used to minimize matrix interference. Method performance was evaluated through calibration, recovery studies, detection limits, measurement uncertainty, and Green Analytical Procedure Index (GAPI) assessment. The optimized method demonstrated excellent linearity (R² > 0.999), with a limit of detection of 0.76 µg/L for seawater. External calibration combined with the optimized furnace program achieved recoveries between 85% and 107% for seawater and 94–102% for diluted hypersaline brine. Standard addition confirmed negligible matrix effects (R² = 0.9995). The combined standard uncertainty was 0.31 µg/L, corresponding to an expanded uncertainty of ± 0.62 µg/L (k = 2). GAPI evaluation classified 13 of the 15 assessment criteria as green. The proposed modifier-free GFAAS method provides accurate and reliable determination of trace cadmium in seawater and hypersaline brine without the use of chemical modifiers. Matrix-specific furnace temperature optimization significantly improves analytical performance while maintaining environmental sustainability, making the method suitable for routine monitoring of hypersaline waters.